i was watching something on youtube ,when my sound went out, which could have been due to the cat using the keyboard for a headrest.i have sound every where else i should , but no idea how to get it back for the youtube.

Also check the speaker icon on the taskbar near where the time is displayed and make sure that it is not muted. A lot of keyboards have mute and volume buttons on them. If the speaker /mixer icon is in mute you should see a red symbol through it or an x see ink below for examples of speaker mute icons